1. Field of the Invention:
The present invention relates to an ion exchange membrane electrolytic cell. More particularly, it relates to an ion exchange membrane electrolytic cell suitable for an electrolysis of water or an aqueous solution of an acid, a base, an alkali metal sulfate, an alkali metal carbonate, or an alkali metal halide and to a process for electrolysis using the same.
2. Description of the Prior Art:
An electroconductive material is referred to as an electric conductive material. An non-electroconductive material is referred to as an electric non-conductive material.
As a process for producing an alkali metal hydroxide by the electrolysis of an aqueous solution of an alkali metal chloride, a diaphragm method has been principally employed instead of a mercury method in order to prevent pollution.
It has been proposed to use an ion exchange membrane in place of asbestos as a diaphragm to produce an alkali metal hydroxide by electrolyzing an aqueous solution of an alkali metal chloride so as to obtain an alkali metal hydroxide having high purity and high concentration.
On the other hand, it has been proposed to save energy in the world. From this viewpoint, it is necessary to minimize the a cell voltage in such technology.
It has been proposed to reduce the cell voltage by improvements in the materials, compositions and configurations of an anode and a cathode and compositions of an ion exchange membrane and the kind of ion exchange group.
It has been proposed to attain an electrolysis by a so called solid polymer electrolyte type electrolysis of an alkali metal chloride wherein a cation exchange membrane of a fluorinated polymer is bonded with gas-liquid permeable catalytic anode on one surface and a gas-liquid permeable catalytic cathode on the other surface of the membrane (British Pat. No. 2,009,795, U.S. Pat. Nos. 4,210,501 and 4,214,958 and 4,217,401).
This electrolytic method is remarkably advantageous as an electrolysis at a lower cell voltage because the electric resistance caused by the electrolyte and electric resistance caused by bubbles of hydrogen gas and chlorine gas generated in the electrolysis can effectively be decreased this has been considered to be difficult to attain in the conventional electrolysis.
The anode and the cathode in this electrolytic cell are bonded on the surface of the ion exchange membrane to be partially embedded. The gas and the electrolyte solution are readily permeated so as to easily remove, from the electrode, the gas formed by the electrolysis at the electrode layer contacting the membrane. Such porous electrode is usually made of a thin porous layer which is formed by uniformly mixing particles which act as an anode or a cathode with a binder, further graphite or other electric conductive material. However, it has been found that when an electrolytic cell having an ion exchange membrane bonded directly to the electrode is used, the anode in the electrolytic cell is brought into contact with hydroxyl ion which is reversely diffused from the cathode compartment, and accordingly, both chlorine resistance and alkaline resistance for anode material are required and an expensive material must be used. When the electrode layer is bonded to the ion exchange membrane, a gas is formed by the electrode reaction between an electrode and membrane and certain deformation phenomenon of the ion exchange membrane causes the characteristics of the membrane to deteriorate. It is difficult to maintain if for a long time in stable condition. In such electrolytic cell, the current collector for electric supply to the electrode layer bonded to the ion exchange membrane should closely contact the electrode layer. When a firm contact is not obtained, the cell voltage may be increased. The cell structure for securely contacting the current collector with the electrode layer is disadvantageously complicated.